1. Field of the Invention
The present invention relates to a seat belt buckle device that secures a tongue plate provided at a seat belt in a vehicle.
2. Related Technology
A seat belt is a safety device for preventing an occupant from bumping against the inner wall of a vehicle and injuring himself in the event of an accident or the like by restraining the occupant's body in the vehicle seat. A seat belt (webbing) is accommodated by winding on a seat belt retractor (retractor) in the center of a B pillar. The webbing unwound upward from the retractor is supported by a seat belt anchorage (anchorage) in the upper portion of the B pillar and folded back to the interior of the vehicle. A tongue plate is attached to the webbing pulled out from the anchorage. When the tongue plate is inserted into the seat belt buckle (buckle), the webbing applied to the chest and stomach of the occupant restraints the occupant's body.
When the tongue plate is inserted into the buckle, the latch hole of the inserted tongue plate is latched inside the buckle by a latch member provided inside the buckle, thereby securing the tongue plate.
Meanwhile, the seat belt can be taken off by the occupant of the vehicle by pushing the release button of the buckle. The pushed release button slides toward the interior of the buckle. As a result, the latch member (or a lock bar that pushes the latch member toward the tongue plate) rises from the tongue plate, the latching of the latch hole is released, and the tongue plate is discharged. Such a configuration of the buckle makes it possible to latch and unlatch the tongue plate easily.
Where a vehicle is subjected to an impact caused by an accident or the like when the seat belt is worn, the webbing is initially locked against pulling out of the retractor. Since the webbing is instantaneously picked up by a pre-tensioner provided in the retractor or the like, the seat belt tightly holds the occupant's body. Where the webbing is picked up by the pre-tensioner or the webbing then receives and stops the load from the occupant, the buckle is pulled to the tongue side. Alternatively, the buckle is pulled in the direction opposite that of the tongue by the action of the buckle pre-tensioner.
When the buckle moves in the direction of pulling from the initial position (tongue direction or the direction opposite thereto), the release button, which can slide inside the buckle, attempts to become stationary in the initial position under the inertia. Further, after the buckle movement has been stopped, the release button attempts to slide under the inertia in the movement direction of the buckle. Under such inertia action, the release button slides into the buckle and the secured tongue plate can be released during an accident. Accordingly, a counterweight acting as a weight with respect to the release button has been provided inside the buckle so as to prevent the release button from sliding under the inertia.
For example, the buckle disclosed in Japanese Patent Application Publication No. 2005-144138 is provided with a latch member, that latches (fixes) the tongue, and a release button, for releasing the latching of the tongue by the latch member, as the elements for fixing and releasing the tongue. Such a buckle is further provided with an inertia lever (counterweight) that is rotatably provided on a rotating shaft and abuts on the release button, thereby preventing the movement of the release button in the release direction thereof (direction in which the abovementioned latch is released). According to Japanese Patent Application Publication No. 2005-144138, the counterweight reliably maintains the latching of the buckle and the tongue even against the inertia force both in the release direction and non-release direction of the release button.
However, in order to dispose the rotatable counterweight, such as described in Japanese Patent Application Publication No. 2005-144138, in a buckle, it is necessary to provide the space allowing the counterweight to rotate in the buckle. This contradicts a recent trend toward miniaturization of the buckle that is aimed at improving the appearance and securing a free space inside the vehicle cabin. In particular, as the counterweight is increased in length, the jumping height thereof during rotation increases and a wider space is necessary for the rotation thereof. Thus, although the counterweight is necessary to prevent the unexpected release of the tongue plate in the event of collision, the presence of the counterweight limits the miniaturization of the buckle.